Grid array packages, such as the Ball Grid Array (BGA) and Land Grid Array (LGA) package layouts provide a surface mount integrated circuit (IC) with a high density of input/output (I/O) connections. The LGA package solution uses contact pads, while the BGA package solution includes solder balls for attachment (e.g., to a printed circuit board (PCB)).
Conventional BGA and LGA package fabrication involves wire bond or flip-chip connection of an IC die to an organic interposer substrate. Custom circuit routing and package I/O layout are available using the organic interposer substrate solution. However, the manufacturing process and materials involved in the organic interposer substrate solution are costly. Also, packages fabricated with an organic interposer substrate have a higher Moisture Sensitivity Level (MSL) than metal leadframe based packages due to the organic substrate's hygroscopic property. In some cases, this leads to handling requirements such as storage within vacuum sealed moisture barrier bags and limited shelf life prior to assembly.
A BGA or LGA package can instead be fabricated upon an etched or stamped leadframe. The leadframe structure, commonly a metal (e.g., copper) strip, includes a die-attach paddle (DAP) at the center of the package. The DAP shifts the I/O connection placement to the periphery of the package. Because the I/O connections are arranged at the periphery of the package, metal leadframe BGA and LGA packages are less tamper resistant. For example, signals at the edges of the BGA and LGA package can easily be probed because they are exposed upon singulation of the package.
The I/O attach lands are supported by and connected to a plating bus frame. The cantilever connection of the attach lands to the plating bus frame limits the distance an attach land can be placed from the plating bus frame. The limitations on the placement of the attach lands can also limit the IC die size range which can be used in the package. For example, if an IC die is small, the wire bonding connections may be sufficiently long to cause wire sweep defects in the molding stage of fabrication.